sectionθ(z,τ)\theta(\mathbf{z},\mathbf{\tau}) of line bundle over Jacobian varietyJ(Στ)J(\Sigma_{\mathbf{\tau}}) in terms of covering coordinates z\mathbf{z} on ℂg→J(Στ)\mathbb{C}^g \to J(\Sigma_{\mathbf{\tau}})